Previous work in the Department of Histology and Histochemistry has been concerned with the tibial growth plate, tibial articular and mandibular condylar cartilages. Observations of the histochemistry, histomorphology and growth patterns of these sites as well as their responses to some nutritional upsets have led to our belief that the condylar and articular cartilages are "embryonic" in structure and exhibit an "adaptive growth potential" unlike the growth plate which is a "primary growth center." Our prime research objective is to further clarify the "adaptive growth potential" of the cartilage of the mandibular condyle, the nasal septum, and that of the tibial articular cartilage. In vitro organ culture techniques, histological, histochemical and radioautographic observations will be utilized. If these methods substantiate the hypothesis that adaptive growth can occur when the sites are in a "hypertrophic form" but can not occur when the cartilages are "non-hypertrophic" we would attempt surgical transplantation in laboratory animals in an effort to mirror current surgical approaches to correcting some cranio-facial anomalies involving the mandibular condyle. Mechanisms of cartilage erosion will also be studied. Chondroclasts will be studied utilizing histochemical, autoradiographic and electron microscopic techniques to attempt to determine their origin and mechanism of erosion. These same tools will be employed to study capillary erosion in a primary growth cartilage, the tibial epiphysis growth plate.